| ISHS Acta Horticulturae 1395: II International Symposium on Precision Management of Orchards and Vineyards
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| Authors: | P.C. Tharaga, L. Dlamini |
| Keywords: | NDVI, remote sensing, validation, water stress |
| DOI: | 10.17660/ActaHortic.2024.1395.3 |
| Abstract:
Fruit tree water consumption associated with growth stages is crucial, and understanding the effects of water stress on tree functionality and the time of the year when stress levels are high can be estimated using remote sensing techniques. Evaluation of NDVI and other parameters leads to understanding the sweet cherry tree stress management under rainfed conditions. The study aimed to determine the water requirements and analyse the water stress levels during different growth stages of sweet cherry trees under rainfed conditions over the eastern Free State in South Africa, using remote sensing. In situ measurements were conducted at the sweet cherry orchard (IONIA Sweet Cherry Farm, IONIA Train Station, Ficksburg, South Africa). There is an imminent need for reliable methods that provide information about the temporal and spatial variability of crop water requirements, allowing farmers to make irrigation decisions at the field scale. This study estimates the evapotranspiration and water stress of sweet cherry orchards in the eastern Free State region of South Africa during 2016/17, 2017/18, 2028/19 and 2019/20 growing seasons by combining a simple surface energy balance model with remote sensing data. A data set of the vegetation index NDVI derived from Landsat-8 and 9 was used to facilitate the estimation of the basal crop coefficient (Kcb), water stress coefficient (Ks), evapotranspiration, and normalised differential vegetation index (NDVI) was derived from remotely sensed canopy thermal-based methods. Verification and validation of the surface energy balance algorithm (SEBAL) model daily evapotranspiration estimates were done using eddy-covariance data collected in the same orchards, yielding an R2≥0.8 and average root mean square errors (RMSE) of 0.96 mm day‑1. It is concluded that the combination of crop evapotranspiration models with remotely sensed data helps determine the stress levels of sweet cherry trees at different growth stages and will be used as an extrapolation tool for agricultural water management and planning in other parts of South Africa where sweet cherries are produced and in need of improving irrigation information from tree to orchard scale. | |
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